KHARTOUM (Reuters) - Sudanese security forces arrested around two dozen opposition members on Thursday who were on their way to deliver a petition to the presidential palace calling for President Omar al-Bashir to step down, a leading member of the opposition said.

This would amount to the largest crackdown against the opposition in one day since protests against Bashir’s rule began two months ago.

Those arrested included Mohamed Mokhtar al-Khatib, the general-secretary of the Communist Party, and three leading members of the Umma Party, said Rabah Sadiq al-Mahdi, daughter of Sadiq al-Mahdi who heads the Umma Party, the largest opposition party.

The spokesman of the Sudanese Professionals’ Association (SPA), the main protest organizer, was also detained.

The authorities could not immediately be reached for comment.

They were arrested while gathering in downtown Khartoum, getting ready to deliver the petition, which demanded the formation of a new transitional government to replace Bashir and his administration.

Sudan has seen near-daily protests since Dec. 19. The demonstrations were triggered by price increases and cash shortages but quickly developed into protests against Bashir’s three-decade rule.

On Thursday Reuters witnessed hundreds of protesters in downtown Khartoum, chanting “peaceful, peaceful against the thieves” and “fall, that’s it”, to send the message that their only demand is Bashir’s fall. Security forces responded with tear gas.

Bashir is wanted by the International Criminal Court over charges of masterminding genocide in the Darfur region, which he denies. He has been lobbying for Sudan to be removed from a list of countries Washington deems state sponsors of terrorism.

The listing has blocked the investment and financial aid that Sudan was hoping for when the United States lifted sanctions in 2017, economists say.

Sudan has been rapidly expanding its money supply in an attempt to finance its budget deficit, causing spiraling inflation and a steep decline in the value of its currency.